Note: Descriptions are shown in the official language in which they were submitted.
PATENT
docket no. 025493-611090
PNEUMATIC TOOL EXHAUST MUFFLER
CROSS REFERENCES TO RELATED APPLICATIONS
This application claims priority to, and the benefit of, U.S. Provisional
Patent Application
Serial No. 62/892,598, filed August 28, 2019, the contents of which are
incorporated herein by
reference in their entirety.
Technical Field of the Invention
The present invention relates generally to pneumatic tools. More particularly,
the present
invention relates to a muffler for a pneumatic tool.
Background of the Invention
Mufflers are often used in exhaust ports of air powered tools (also referred
to as
pneumatic tools) to reduce the amount of noise generated by the exhaust of the
tools. Air
powered tools can produce high noise levels in excess of 80 dB, particularly
when used in large
numbers in a confined spaces, such as on production lines. The noises
generated by the exhaust
are derived from pass frequencies of air passing over turbine motors that
drive the air tools and
high speed of the exhaust air flow. In addition, noise is generated by
vibration-radiated sound
produced by the moving parts of the tool. The noises generated by the tool are
a significant
contributor to workplace injuries, such as hearing loss. In addition, loud
noises over long periods
of time induce operator fatigue.
Current solutions muffle exhaust noise of pneumatic tools by placing sponge
like or
fibrous materials in the exhaust ports. However, these materials cause the air
flow to be
restricted, which slows the air flow and converts kinetic and acoustic energy
into thermal energy,
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thereby reducing the amount of noise generated by the exhaust. A consequence
of adding these
materials to the exhaust ports is that the air flow is restricted and the tool
is thus throttled.
Summary of the Invention
The present invention broadly comprises a muffler for air powered tools that
minimizes
pass through restriction of exhaust air. Noise generated by the exhaust air is
dampened or
mitigated by incorporating one or more cavities within walls of the exhaust
path or in side
branches of the exhaust path to act as Helmholtz resonators. The cavities may
be dimensioned to
be quarter-wavelength, half-wavelength, or an integer or opposing wavelength
of target
frequencies of the noise generated by the exhaust. Typically, target exhaust
noise frequencies of
pneumatically operated power tools range from 50 Hz to 10 kHz.
Accordingly, the present invention improves upon muffler technology for air
powered
tools by presenting a solution that does not restrict operation of the tool by
restricting the exhaust
path. By utilizing cavities located in the wall or in side branches of the
exhaust path, the targeted
frequencies can be canceled or dissipated while still allowing the airflow to
pass relatively
unrestricted through the exhaust path. Further, by locating one or more
cavities in a thin wall
cross section and the requisite dimensions of the cavities, the cavities can
have a circuitous path.
The present invention broadly comprises a high pass muffler disposed in an air
exhaust
passage of a pneumatic tool. The muffler includes an outer body with a channel
having a
terminal end and an inner body disposed within the outer body that includes an
aperture located
proximate to the terminal end.
In another embodiment, the present invention broadly comprises a pneumatic
tool
including an air intake passage, an air exhaust passage, and a muffler
disposed in the air exhaust
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passage. The muffler includes an outer body with a channel having a terminal
end and an inner
body coupled to the outer body and that includes an aperture located proximate
the terminal end.
Brief Description of the Drawings
For the purpose of facilitating an understanding of the subject matter sought
to be
protected, there are illustrated in the accompanying drawings embodiments
thereof, from an
inspection of which, when considered in connection with the following
description, the subject
matter sought to be protected, its construction and operation, and many of its
advantages should
be readily understood and appreciated.
FIG. 1 is a perspective view of a housing of an air powered tool incorporating
an
embodiment of the present invention.
FIG. 2 is bottom plan view showing the housing of the air powered tool
incorporating an
embodiment of the present invention of FIG. 1.
FIG. 3 is a perspective view showing a muffler according to an embodiment of
the
present invention.
FIG. 4 is a perspective view showing an inner body of the muffler of FIG. 3.
FIG. 5 is a perspective view showing an outer body of the muffler of FIG. 3.
FIG. 6 is a perspective view of the muffler of FIG. 3 showing the inner body
and the
outer body of the muffler in a disassembled state.
FIG. 7 is a perspective view a channel of an outer body of a muffler according
to an
embodiment of the present invention.
FIG. 8 is a perspective view showing a portion of a muffler according to an
embodiment
of the present invention.
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FIG. 9 is a perspective view of the muffler of FIG. 8 showing a portion of the
inner body
and a portion of the outer body of the muffler in a disassembled state.
Detailed Description of the Embodiments
While this invention is susceptible of embodiments in many different forms,
there is
shown in the drawings, and will herein be described in detail, a preferred
embodiment of the
invention with the understanding that the present disclosure is to be
considered as an
exemplification of the principles of the invention and is not intended to
limit the broad aspect of
the invention to embodiments illustrated. As used herein, the term "present
invention" is not
intended to limit the scope of the claimed invention and is instead a term
used to discuss
exemplary embodiments of the invention for explanatory purposes only.
Referring to FIGs. 1 and 2, a motor body 100 with an air intake passage 102
and an air
exhaust passage 104 is shown. Air flows through the air intake passage 102 to
power a motor
rotor, such as a vane pump (not shown), which results in blade pass
frequencies that create an
audible whine-like noise. The noise frequencies are a function of the number
of vanes in the vane
pump (i.e., motor size) and an applied magnitude of air pressure (i.e., air
velocity). The noise
frequencies vary from 50 Hz to 10 kHz.
Referring to FIGs. 3-8, a muffler 106 is disposed, at least partially, within
the air exhaust
passage 104. The muffler 106 is, for example, a relatively tubular structure
and can be
constructed in two parts, where an outer surface of an inner body (also
referred to as an inner
.. tube) 108 couples or is interference fit to an inner surface of an outer
body (also referred to as an
outer tube) 110. While the muffler 106 is illustrated as a cylindrical tube,
the cross section of the
outer body 110 can be shaped to correspond with an inner surface of the air
exhaust passage 104
of FIGs. 1 and 2.
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In an embodiment, the inner body 108 is constructed in halves adapted to be
assembled
into a singular body. Similarly, in an embodiment, the outer body 110 is
constructed in halves
adapted to be assembled into a singular body. Once assembled, the outer body
110 is adapted to
receive the inner body 108. Alternately, the outer body 110 and the inner body
108 are
respectively formed as singular bodies. The outer body 110 and the inner body
108 can be
constructed of polymers, ceramics, and/or organic materials, for example.
In an embodiment, the inner body 108 includes at least one aperture 112
adapted to allow
exhaust air to flow therethrough and into at least one channel 114 disposed in
the outer body 110.
The aperture 112 is located proximate to a terminal end 116. The channel 114
may follow a
circuitous path having angular corners, as illustrated in FIGs. 5 and 7,
and/or a curved path
without angular corners (not shown). The channel 114 acts as a Helmholtz
resonator.
The dimensions of the channel 114 include a depth of the channel 118, a width
of the
channel 120, and a length of the channel 122, as illustrated in FIG. 7. The
dimensions of the
aperture 112 include a depth 124, or wall thickness of inner body 108, and
opening dimensions
126 and 128. A cross-sectional area of the opening of the aperture 112 is
defined by the
dimensions 126 and 128, as illustrated in FIG. 8. The aperture 112 may have
other cross-sections
besides a square, for example, the cross-section may have a round, a polygon,
or an amorphous
shape.
The dimensions of the aperture 112 and the volume and shape of the channel 114
determine the performance specifications of the muffler 106, and may be
altered such that the
muffler is tuned to resonate at a quarter wavelength, a half wavelength, or a
full wavelength of
certain target frequencies of noise generated by blade pass frequencies. The
target frequencies
can range from 50 Hz to 10 kHz.
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In another embodiment, the muffler 106 is not contained entirely in the air
exhaust
passage 104, such that a portion protrudes past a terminus of the motor body
100. In this
configuration, the aperture 112 and the channel 114 may extend into larger
volumes, additional
cavities, and/or side branches that are not contained within the walls of the
outer body 110 of the
muffler 106.
Accordingly, the muffler 106 does not throttle the tool by restricting the
exhaust path. By
utilizing the channel 114 located in the outer body 110, the targeted
frequencies can be canceled
or dissipated while still allowing the airflow to pass relatively unrestricted
through the air
exhaust passage 104.
As used herein, the term "coupled" and its functional equivalents are not
intended to
necessarily be limited to direct, mechanical coupling of two or more
components. Instead, the
term "coupled" and its functional equivalents are intended to mean any direct
or indirect
mechanical, electrical, or chemical connection between two or more objects,
features, work
pieces, and/or environmental matter. "Coupled" is also intended to mean, in
some examples, one
object being integral with another object.
The matter set forth in the foregoing description and accompanying drawings is
offered
by way of illustration only and not as a limitation. While particular
embodiments have been
shown and described, it will be apparent to those skilled in the art that
changes and modifications
may be made without departing from the broader aspects of the inventors'
contribution. The
actual scope of the protection sought is intended to be defined in the
following claims when
viewed in their proper perspective based on the prior art.
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